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| Rev | Author | Line No. | Line |
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| 2 | pj | 1 | /* @(#)s_logb.c 5.1 93/09/24 */ |
| 2 | /* |
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| 3 | * ==================================================== |
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| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 5 | * |
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| 6 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 7 | * Permission to use, copy, modify, and distribute this |
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| 8 | * software is freely granted, provided that this notice |
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| 9 | * is preserved. |
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| 10 | * ==================================================== |
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| 11 | */ |
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| 12 | |||
| 13 | #ifndef lint |
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| 14 | static char rcsid[] = "$\Id: s_logb.c,v 1.2.6.1 1997/02/23 11:03:20 joerg Exp $"; |
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| 15 | #endif |
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| 16 | |||
| 17 | /* |
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| 18 | * double logb(x) |
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| 19 | * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. |
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| 20 | * Use ilogb instead. |
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| 21 | */ |
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| 22 | |||
| 23 | #include "math.h" |
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| 24 | #include "math_private.h" |
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| 25 | |||
| 26 | #ifdef __STDC__ |
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| 27 | double __generic_logb(double x) |
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| 28 | #else |
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| 29 | double __generic_logb(x) |
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| 30 | double x; |
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| 31 | #endif |
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| 32 | { |
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| 33 | int32_t lx,ix; |
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| 34 | EXTRACT_WORDS(ix,lx,x); |
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| 35 | ix &= 0x7fffffff; /* high |x| */ |
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| 36 | if((ix|lx)==0) return -1.0/fabs(x); |
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| 37 | if(ix>=0x7ff00000) return x*x; |
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| 38 | if((ix>>=20)==0) /* IEEE 754 logb */ |
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| 39 | return -1022.0; |
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| 40 | else |
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| 41 | return (double) (ix-1023); |
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| 42 | } |